The present invention relates to novel compounds which are useful as active ingredients of medicaments such as angiogenesis inhibitors and antitumor agents.
Recently, angiogenesis has been elucidated as an important physiological phenomenon in proliferation and metastasis of various progressive solid cancers. The angiogenesis is completed through steps including, for example, (1) stimulation by vascular endothelial growth factor (VEGF) secreted from tumor cells; (2) disengagement of peritheliocyte or decomposition or digestion of extracellular matrix such as basal membrane; (3) migration and proliferation of vascular endothelial cells; (4) formation of tubule by the endothelial cells, formation of basal membrane, and maturation of blood vessel. In tumorous angiogenesis, the generated new vessels have a role of supplying oxygen and nutriment to tumors to accelerate their growth and serving as a route for infiltration and metastasis of tumor cells to other tissues.
Among them, the vascular endothelial growth factor has variety of functions in the blood, vessel, and coagulation system such as for induction of proliferation and survival and maintenance of vascular endothelial cells, acceleration of blood vessel permeability, platelet migration, and chemotaxis of macrophage, as well as for angiogenesis. Therefore, novel compounds inhibiting chemotaxis that is induced by VEGF derived from vascular endothelial cells are expected to be useful as angiogenesis inhibitors, antitumor agents, agents inhibiting metastasis, and agents for treatment of rheumatic arthritis (Eur. J. Cancer, 32A, 2534-2539, 1996; Nature Med., 1, 27-31, 1995, Immunity, 12, 121, 2000).
In addition, angiogenesis inhibitors are potential therapeutic medicament for diabetic retinopathy as one of complications of diabetic vascular diseases. At present, treatments for diabetic retinopathy are given basically as symptomatic treatments, and since late treatments often result in ablepsia, effective medicaments are desired which are effective in preventive and therapeutic treatments. In recent years, angiogenesis inhibitors based on variety of modes of actions have been clinically developed. Under the circumstances, novel compounds as potential lead compounds have always been desired strongly.
An object of the present invention is to provide novel compounds which exert angiogenesis inhibitory activity, antitumor activity, and metastasis inhibitory activity by inhibiting chemotaxis of vascular endothelial cells. Another object of the present invention is to provide a method for preparing a novel compound having the aforementioned features and a medicament comprising said compound as an active ingredient.
The inventors of the present invention conducted various studies to achieve the foregoing objects. As a result, they found that novel compounds isolated from a culture of a microorganism belonging to genus Neosartorya, a filamentous fungus, has angiogenesis inhibitory activity and antitumor activity. The present invention was achieved on the basis of the findings.
The present invention thus provides a compound represented by the following formula (I) or a salt thereof. 
According to preferred embodiment of the invention, provided is a compound represented by the following formula (II) or a salt thereof. 
According to another aspect of the present invention, provided is a medicament which comprises the aforementioned compound or a physiologically acceptable salt thereof as an active ingredient. The medicament can be used as a medicament for preventive and/or therapeutic treatment of diseases with excess angiogenesis or diseases resulting from excess angiogenesis, therapeutic treatment of malignant tumors, inhibition of metastasis of malignant tumors, preventive and/or therapeutic treatment of diabetes and complication of diabetes, and preventive and/or therapeutic treatment of inflammatory diseases. The present invention further provides an angiogenesis inhibitor which comprises the aforementioned compound or a physiologically acceptable salt thereof as an active ingredient; an inhibitor against chemotaxis of vascular endothelial cells which comprises the aforementioned compound or a physiologically acceptable salt thereof as an active ingredient; an antitumor agent which comprises the aforementioned compound or a physiologically acceptable salt thereof as an active ingredient; and an inhibitor against metastasis of malignant tumors which comprises the aforementioned compound or a physiologically acceptable salt thereof as an active ingredient. The angiogenesis inhibitor can be administered, for example, for preventive and/or therapeutic treatment of diabetic retinopathy.
As a further aspect of the present invention, there is provided a method for preparing the aforementioned compound or a salt thereof, which comprise the step of separating and collecting the aforementioned compound or a salt thereof from a culture obtained by culturing a microorganism belonging to genus Neosartorya which can produce the aforementioned compound. The present invention also provides a method for therapeutic treatment of malignant tumors which comprises the step of administering a therapeutically effective amount of the aforementioned compound or a physiologically acceptable salt thereof to a mammal including a human; a method for inhibition of metastasis of malignant tumors which comprises the step of administering a therapeutically effective amount of the aforementioned compound or a physiologically acceptable salt thereof to a mammal including a human; a method for angiogenesis inhibition in tumor tissues which comprises the step of administering a therapeutically effective amount of the aforementioned compound or a physiologically acceptable salt thereof to a mammal including a human; a method for suppression of abnormal acceleration of angiogenesis which comprises the step of administering a therapeutically effective amount of the aforementioned compound or a physiologically acceptable salt thereof to a mammal including a human; a method for preventive and/or therapeutic treatment of diabetic retinopathy which comprises the step of administering a therapeutically effective amount of the aforementioned compound or a physiologically acceptable salt thereof to a mammal including a human; and a method for inhibition of chemotakis of vascular endpthelial cells which comprises the step of administering a therapeutically effective amount of the aforementioned compound or a physiologically acceptable salt thereof to a mammal including a human.
The compound represented by the formula (I) or (II) according to the present invention (either or both of them are hereinafter referred to as xe2x80x9cthe compound of the present inventionxe2x80x9d) has asymmetric carbon atoms, and stereoisomers such as optical isomers and diastereomers based on the asymmetric carbon atoms exist. The stereoisomers in a pure form as well as mixtures of any stereoisomers or racemates fall within the scope of the present invention. The compound of the present invention has plural olefinic double bonds, and geometrical isomers based on each double bond may exist. The geometrical isomers in a pure form as well as mixtures of any geometric isomers fall within the scope of the present invention. An example of a preferred geometrical isomer is the compound represented by the formula (II).
The compound of the present invention in a free form, as well as a salt of the aforementioned compound, preferably a physiologically acceptable salt, falls within the scope of the present invention. The form of the salt is not particularly limited. A salt such as a sodium salt may sometimes be formed with the hydroxyl groups in the molecule. A hydrate or a solvate of the aforementioned compound or a salt thereof also falls within the scope of the present invention. A preferred example of the compound of the present invention includes the compound represented by the formula (II). This particular compound may sometimes be referred to as xe2x80x9cRKB-3134Axe2x80x9d in the specification.
A method for preparing the compound of the present invention is not particularly limited. Examples include a method for separating and collecting the target compound from a culture of a microorganism which can produce the compound of the present invention (extracting method), or a method for chemically synthesizing the target compound by using a compound having a similar structure as a starting material which is contained in a culture of a microorganism (synthetic method or semi-synthetic method). In the extracting method, a microorganism that can produce the compound of the present invention is cultured in a medium under conditions which are used in an ordinaiy fermentation production, and then the target product can be separated and collected from the resulting culture. An example of the microorganism that can produce the compound of the present invention includes BAUA 3134 strain belonging to genus Neorsartorya. This microorganism has been deposited in Patent and Bio-Resource Center of National Institute of Advanced Industrial Science and Technology (Chuo-6, 1-1-1, Higashi, Tsukuba, Ibaraki, Japan) with the ascension number of FERM P-18455 on Aug. 13, 2001, and said deposition has been transferred to the international deposition under Budapest Treaty with the accession number of FERM BP-8189 on Sep. 19, 2002.
A medium for preparing the compound of the present invention is not particularly limited, and any of synthetic mediums or natural mediums can be suitably used so long as they appropriately contain carbon resources, nitrogen resources, and inorganic salts. If necessary, mediums may be added with vitamins and other nutrient substances.
As the carbon sources, one or more kinds of resources may suitably be chosen and used in consideration of auxotrophy of a microorganism from general carbon sources, for example, sugars such as glucose, maltose, fructose, sucrose, and starch, alcohols such as glycerol, and mannitol, amino acids such as glycine, alanine, and asparagine, and oils and fats such as soy bean oil and olive oil. Examples of the nitrogen sources include organic nitrogen-containing compounds such as soy bean powder, corn steep liquor, beef extract, peptone, yeast extract, amino acid mixtures, and fish powder, and inorganic nitrogen compounds such as ammonium salts and nitrates, and one or more kinds of the resources may suitably be chosen and used in consideration of auxotrophy of a microorganism. As the inorganic salt, for example, calcium carbonate, sodium chloride, potassium chloride, magnesium sulfate, cupper sulfate, manganese chloride, zinc sulfate, cobalt chloride, and various phosphates may be added, if necessary. A defoaming agent such as vegetable fats and polypropylene alcohols can also be added, if necessary.
A cultivation temperature may appropriately chosen and changed within a range that allows growth of a microorganism and production of the compound of the present invention. Preferred cultivation temperature is from 10xc2x0 C. to 32xc2x0 C., and more preferably from 20xc2x0 C. to 28xc2x0 C. Initial pH is preferably from about 6 to 8, and cultivation period of time is generally about one day to a few weeks. The cultivation may be terminated when a produced amount of the compound of the present invention reaches to that can be collected, preferably reaches to the maximum amount. A cultivation method is not particularly limited, and any method ordinarily used can be suitably used such as solid layer cultivation and normal stirring cultivation.
In order to separate and collect the compound of the present invention from the culture liquid, any technique ordinarily used for collecting microbial metabolites can be appropriately applied. Examples include chromatography with various ion exchange resins, nonionic adsorbing resins, gel filtration chromatography, or adsorbent such as activated charcoal, alumina, and silica gel, or high performance liquid chromatography, or crystallization, concentration under reduced pressure, or lyophilization, which techniques can be used alone or in appropriate combination thereof, or repeatedly.
The compound of the present invention has excellent angiogenesis inhibitory action and antitumor activity. Accordingly, the compound of the present invention is useful as an active ingredient of a medicament for preventive and/or therapeutic treatment of various diseases in which excess angiogenesis is involved as one of causes of onset thereof. The medicament of the present invention can be used for mammals including human, for example, as a medicament for preventive and/or therapeutic treatment of diabetic vascular complications, diabetic retinopathy, articular rheumatism, rheumatoid arthritis, diabetes, arteriosclerosis, ulcerative colitis, psoriasis, angiopoietic glaucoma, inflammatory diseases and the like, as well as an antitumor agent or a tumor metastasis inhibitor.
A route of administration, a dosage form, and a dose of the medicament comprising the compound of the present invention as an active ingredient can be appropriately chosen depending on a purpose of administration. For example, the route of administration of the medicament comprising the compound of the present invention as an active ingredient may be oral administration or parenteral administration. Examples of the dosage form include oral preparations such as tablets, powders, capsules, granules, extracts, and syrups, and parenteral preparations such as injections, drip infusions, and suppositories. These preparations can be manufactured according to known methods by using pharmaceutically acceptable additives such as excipients and binders. A dose of the medicament comprising the compound of the present invention as an active ingredient may usually be from about 0.1 to 1 g, preferably from about 1 mg to 100 mg, per day for oral administration for an adult, and from about 0.01 to 100 mg, preferably from about 0.1 mg to 20 mg, per day for parenteral administration for an adult, which may be increased or decreased depending on the age and body weight of a patient, type of a disease, a degree of symptom and the like. The aforementioned dose can be administered once a day or several times a day as divided portions. However, a dose out of the aforementioned range can be administered, if necessary.
When the compound of the present invention is used as a reagent, the compound can be used by dissolving in an organic solvent or a water-containing organic solvent. For example, cell growth can be inhibited by direct application to various culture cell systems. Examples of usable organic solvent include methanol, dimethyl sulfoxide and the like. Examples of reagent forms include solid preparations such as powders, or liquid preparations dissolved in an organic solvent or a water-containing organic solvent. When the aforementioned compound is used as a reagent for exerting angiogenesis inhibitory action, an effective amount is generally from 0.3 to 30 xcexcg/ml. An appropriate amount may differ depending on a type of a culture cell system and a purpose to use the reagent, however, the amount can suitably be chosen by one of ordinary skill in the art. The amount out of the aforementioned range can be applied, if necessary.